The present disclosure relates to interior permanent magnet (or xe2x80x9cIPMxe2x80x9d) machines such as, for example, an IPM motor. IPM machines have been used in various applications in the past, but the use of such machines in applications requiring a high degree of torque from a relatively small machine or low-noise has been limited by certain characteristics of IPM machines.
For example, because IPM machines utilize a rotor that contains a number of interior permanent magnets, there is a tendency for magnetic flux produced by the magnets to circulate between two adjacent magnets. This intra-magnet flux circulation tends to reduce the overall torque output of the machine because the magnetic flux that circulates between the magnets is not readily available for torque production. In addition to reducing the overall torque output of the machine, this intra-magnet flux circulation also tends to decrease the overall efficiency of the machine.
Further, IPM motors because of their use of discretely positioned interior permanent magnets tend to have a degree of unwanted torque ripple or torque variation often known as xe2x80x9ccogging torque.xe2x80x9d Such cogging torque can produce unwanted noise and/or vibrations and can reduce the overall efficiency of the machine.
A further characteristic of IPM machines that potentially limits the torque output and efficiency of such machines is the ability to get current into the windings of such machines. The ability to get current into the machine is an important factor in producing torque and having an efficient machine as the torque out of the machine will correspond closely to the amount of current that is put into the phase windings and the speed at which the current its placed in the phase windings will impact the efficiency of the machines. Typically, IMP motors have had a construction that generally results in the phase windings of such machines having a relatively high inductance. This relatively high inductance has tended to limit the ability to get current in to the windings of such machines. The present disclosure described several embodiments of IPM machines that are designed to address the described, and other, limiting characteristics of IPM machines to provide an improved IPM machine that has, for example, a relatively high torque output, high efficiency and low cogging torque.
In accordance with one exemplary embodiment constructed in accordance with certain teachings of the present disclosure, a high torque density interior permanent magnet machine for use in an appliance is provided that includes a stator assembly defining a plurality of stator teeth, a plurality of concentrated phase windings positioned about the stator teeth, a rotor assembly positioned within the interior bore and a plurality of magnets positioned within the interior of the rotor.
In accordance with another exemplary embodiment constructed in accordance with certain teachings of the present disclosure, a washing machine is provided that includes an interior permanent magnet motor including a stator assembly, a plurality of phase windings positioned within the stator, where each phase winding comprises a plurality of coils and wherein each coil is wound about a single stator tooth, a rotor defining a plurality of magnet retention slots, each magnet retention slot defining generally parallel upper and lower surfaces; and a plurality of block magnets, each block magnet being positioned within a magnet retention slot and an agitator or impeller (which may be a separate agitator element, an impeller element, a mechanism for moving the drum or other suitable means for moving the clothes in the machine) driven by the motor.
In accordance with yet another exemplary embodiment constructed in accordance with certain teachings of the present disclosure a washing machine is provided that includes an interior permanent magnet motor including a stator assembly defining an interior bore, the stator assembly defining a plurality of stator teeth, a plurality of phase windings positioned within the stator, where each phase winding comprises a plurality of coils and wherein each coil is wound about a single stator tooth; a rotor including a plurality of interior permanent magnets; an agitator or impeller coupled to the motor, and a tub coupled to the motor; wherein the motor drives the agitator or impeller during the wash cycle and the agitator or impeller and the tub during the spin cycle, and when the rotor is rotating, the rotational speed of the agitator or impeller is equal to the rotational speed of the motor.
In accordance with still another exemplary embodiment constructed in accordance with certain teachings of the present disclosure, an interior permanent magnet motor is provided that includes a stator defining a stator bore, a rotor positioned within the stator bore, the rotor including a plurality of interior permanent magnets, at least one phase winding positioned within the stator, wherein the phase winding a plurality of winding coils with each winding coil being wound about a single stator tooth, and wherein two of the coils are wound about a first pair of adjacent stator teeth, two of the coils are diametrically opposed and the coils are wound such that when current is flowing through the at least one phase winding, adjacent coils establish electromagnets of opposing polarities and diametrically opposed coils establish electromagnets of opposing polarities.
Other aspects of the present disclosure will be apparent from a review of the disclosure, the figures and the claims.